DETERMINATION OF SUBSURFACE PERMEABEL ZONE IN SOUTHERN WAYANG WINDU GEOTHERMAL FIELD BASED ON SURFACE RADON-222 MEASUREMENT

• Main Author: Yuliyanto, Eksan
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/54801
• Institution: Institut Teknologi Bandung

The problems that arise in the exploitation of geothermal one of them is the prediction of a permeable rock. Permeable rocks are one of the most important elements in the analysis of potential determination of geothermal field to prospect of drilling location of exploitation. One method of estimating the subsurface permeable zone is by analyzing the soil-gas Radon on the surface. The primary data Radon-222 gas concentrations are obtained from direct measurements in the field with Durridge RAD7 tools. Measurements were made in 5 measurement cycles over the timeframe of October 2016 to May 2017. The data taken at each measurement point were 10 data with each data retrieval for 5 minutes. Gas concentration data obtained then processed by Ordinary Kriging method to get the pattern of its distribution. The distribution pattern obtained is then correlated with several analysis parameters. Analytical parameters used include regional fault, subsurface structure, manifestation, lithology, topography and lineament. The correlation result is an overlay map between the Radon-222 concentration distribution map with each parameter. Distribution of high concentrations of surface Radon-222 gas is present in the northern areas of the study, including the measurement points K18, K22, K17, K19, and K30. While the low concentration dominates in the southern area of the study area includes measurement points K23, K26, and K28. There is a close relationship between the Radon-222 concentration on the surface regional fault issued by Alzwar et al (1992), the subsurface structure released by Star Energy (2014), and the manifestations that exist around the study area. This indicates that the concentration of Radon-222 on the surface is strongly influenced by the presence of geological structures that give rise to a subsurface permeable zone. Where the permeable zone becomes a Radon-222 pathway to get out to the surface.